Gonsalves M, Macpherson J V, O'Hare D, Winlove C P, Unwin P R
Department of Chemistry, University of Warwick, Coventry, UK.
Biochim Biophys Acta. 2001 Nov 15;1524(1):66-74. doi: 10.1016/s0304-4165(00)00142-2.
Scanning electrochemical microscopy (SECM) has been used in the induced transfer (SECMIT) mode to image the permeability of a probe cation, methyl viologen (MV(2+)), in samples of articular cartilage. An ultramicroelectrode (UME), scanned just above the surface of a sample, is used to amperometrically detect the probe solute. The resulting depletion of MV(2+) in solution induces the transfer of this cation from the sample into the solution for detection at the UME. The current provides quantitative information on local permeability, provided that the sample-UME distance is known. It is shown that the necessary topographical information can be obtained using the amperometric response for the oxidation of Ru(CN)(4-)(6), which does not permeate into the cartilage matrix. This procedure was validated by marking samples in situ, after electrochemical imaging, with subsequent examination by ex situ interferometry and optical microscopy. Wide variations in the permeability of MV(2+) have been detected by SECMIT. These observations represent the first demonstration of the inhomogeneous permeability of a cation in cartilage on a micrometre scale. The permeability maps show similar features to the proteoglycan distribution, identified by toluidine blue staining, and it is likely that proteoglycans are the main determinant of MV(2+) permeability in articular cartilage.
扫描电化学显微镜（SECM）已被用于诱导转移（SECMIT）模式，以成像关节软骨样本中探针阳离子甲基紫精（MV(2+)）的渗透性。在样品表面上方扫描的超微电极（UME）用于安培检测探针溶质。溶液中MV(2+)的消耗导致该阳离子从样品转移到溶液中，以便在UME处进行检测。如果样品与UME的距离已知，电流可提供有关局部渗透性的定量信息。结果表明，使用对不渗透软骨基质的Ru(CN)(4-)(6)氧化的安培响应，可以获得必要的地形信息。在电化学成像后，通过原位标记样品，随后进行非原位干涉测量和光学显微镜检查，验证了该程序。通过SECMIT检测到MV(2+)的渗透性存在很大差异。这些观察结果首次证明了阳离子在软骨中微米尺度上的不均匀渗透性。渗透性图谱显示出与通过甲苯胺蓝染色确定的蛋白聚糖分布相似的特征，并且蛋白聚糖很可能是关节软骨中MV(2+)渗透性的主要决定因素。
